The present invention relates to a centrifugal impeller for sandblasting installations, including a rotatively driven centrifugal impeller wheel and a plurality of radially oriented projecting blades mounted on one side surface of the impeller wheel by associated dovetail joints and locked in position by respective spring members.
In heretofore known centrifugal impellers of the above-indicated type which may be termed so-called "single-disc" wheels, a plurality of projecting blades are mounted on only one side surface of the impeller wheel. Each mounting assembly for a projecting blade includes a dovetail joint, and the projecting blade is locked in position by a thrust bolt extending through a threaded bore in the centrifugal impeller wheel and tightened against the dovetail key of the projecting blade. Each thrust bolt includes a hexagonal recess for tightening and releasing respectively the bolt. This recess must be protected against the blasting medium by inserting an additional plug member. The inner end of the thrust bolt must be provided with a cylindrical end portion, and the dovetail key of the projecting blade must be provided with a corresponding recess for receiving the inner end of the bolt and locking the projecting blade in position. This type of mounting is rather complicated and relatively expensive. In case of improper handling it may become very difficult to release the bolts.
In so-called two-disc wheels it has already been suggested to employ springs for mounting and locking the projecting blades. With such an arrangement, these springs are freely exposed on one side of the projecting blades, with the result that centrifugal impellers of this type may only be used in one direction of rotation. An operation in the opposite direction of rotation is not possible since the side surfaces at which are arranged the unprotected springs may not be exposed to the blasting medium.